Supermarket and petrol station giant Tesco is taking its Big Brother technology to a new level.

Our biggest supermarket chain is to install technology that scans its shoppers' faces.

The company claims this will just be in order to display tailored video advertising on screens at its petrol stations.

The system will recognise facial characteristics that determine gender and age. These will be matched to targeted video adverts.

The system, developed by a company owned by Lord Sugar, will be firstly installed at all Tesco's 450 UK petrol stations.

However a spokesman for Sugar's company has said: "Our plans are to expand the screens into as many supermarkets as possible."

That opens up the possibility of combining the photo recognition with the vast amount of customers' personal data Tesco already collects, holds and distributes.

Already one in four people in Britain hold a Tesco Clubcard and the amount of information this allows Tesco to hold on its customers is one key reason for the stores amazing domination of the market.

The Clubcard enables the store to gather information on their customers' lifestyles.

It knows if you smoke, if, and how much, you drink and even, if you buy your condoms from the store, all about your sex life.

The sophisticated data processing can find out an incredible amount from a customer's buying habits.

Not only does this let Tesco bosses know which range of products to stock in different areas but the supermarket can also sell the information to a range of retailers and to major manufacturers.

The use of this level of data can easily lead to abuse. In the US supermarkets using similar systems have got into trouble.

They discovered that certain buying patterns could even let them diagnose pregnancy. They started to send their special offers to expectant mums.

However some of them were underage and hadn't yet told their parents. In some cases this has led not just to complaints but also legal action.

Privacy campaigners are horrified by the implications of Tesco's new photo system.

Nick Pickles of Big Brother Watch told us: "Scanning customers as they walk through the store without customers ever giving permission for them to be scanned in that way ... There's a huge consent issue there."

Tesco has long dominated the country's high streets and out-of-town shopping centres to such an extent that more than 100 organisations, from Friends of the Earth to the Women's Institute, have already called on the supermarket giant to be curbed.

Up and down the country Tesco has been rightly blamed for the dwindling number of independent butchers, grocers and corner shops and the decline of town and village high streets.

These actions have made it very unpopular, indeed hated.

Tesco has been fighting back to polish its tarnished reputation and regain what it believes is its natural share of the market.

Now, in desperation, it is greedily extending its Big Brother tactics to try to seize an even bigger share of the pie.

If you must shop at Tesco just don't forget to smile nicely as you go past the camera.